This happened to me repeatedly with multiple songs with StudioOne4. Not just drums, but most often drums, & it happened like some of you have mentioned, after I hadn't touched it for a couple months. After losing some great music, these days, if I'm going to be away for even a week, I just burn everything I'm working on, however it sounds whenever I have to quit working. At least that way I have an audio image to work with. It sucks to have to put your songs back together like a puzzle... a second time, but as long as you're in the practice of saving/renaming any vst patches that you've heavily modified that are used in your song, it's doable. If not, you're stuck with a permanent remix. Good luck w/that, because you might actually end up with a better song, but maybe not... This actually lead to a lot better file management practices for me, but it was a hassle. Since I've upgraded to 6, I haven't had this issue, but it's also only been about 5 weeks, & I've been active the whole time, so the conditions haven't been met, but I'm commenting in hopes that someday, if more people comment, maybe Presonus will do something, although I suspect there's not much they can do, because they don't know why this is happening.